What Must Be Done
by Soomin
Summary: Zangetsu notices that his boy is getting stronger with every fight, and he worries about their future together. When Ichigo loses his fight with Kenpachi Zaraki, he would rather have the boy simply sit there until the end of time than rather watch him continue to fight. The Hollow has different plans.


" _Let me out of here so I can fix myself and help that idiot of a king win!"_ the Hollow screamed from within him. For a moment, Zangetsu almost felt guilty abusing the Hollow's charity. He hadn't intended to be the source of Ichigo's power for this long, and he certainly hadn't predicted the Hollow would let him be on the throne for this long either. However, when the opportunity came up so that Ichigo would no longer have to fight, he wasn't going to do anything to stop his original goal. After all, the Hollow could not heal the blade without his permission.

" _Yhwach, I swear, if you let this boy die,"_ the Hollow warned, as if he could honestly do anything about it.

"Hollow," the old man addressed, "why do you care so much about this boy? Even after learning your name, he has yet to come to talk to us. He uses you instead of fighting with you. This boy seems hardly worthy of your power." It was true. He has heard tale that Shinigami and zanpakutou should fight as one, not as two. The boy has only just learned the name and seemed to think he had all the power in the world.

" _That's because you've been a shitty horse,_ " the Hollow explained with a growl, _"guiding the king into battles he can't win or refusing to help when he needed you! If I was there, I would make sure that he's going as cavalry, not as a pathetic foot soldier,"_ The Hollow exclaimed as he panicked at the rate the boy was losing consciousness. The old man paused, confused at the fact that clouds had begun to form overhead.

"You have the ability to at least heal his physical wounds from there, do so now. It will be at the cost of his resolve to fight, but that is no worry on me. If you want the boy to live, I suggest you do it before he breathes his last breath of air," Yhwach mocked, hiding his worry so that the Hollow will actually hurry up and help the boy. He anticipated resistance to his methods, but he didn't think the Hollow would actually risk the boy's life when he was so close to death.

" _I don't want him to live; I want him to win."_

The old man scoffed at the Hollow's bloodlust. He wondered if this was where Ichigo got his desire to settle argument with blood instead of intellectual conversation. To win, to live, they both had the same meaning to him.

It was then that he felt the first drop. Overhead, the clouds had gotten darker, and the rain began to fall.

Yhwach often wondered if the zanpakutou of other wielders ever experienced different weather conditions. He sometimes joked with the Hollow it was due to Ichigo's teenage hormones that they experienced so many weather conditions. However, it was the rain that he hated the most. Being pelted by these droplets and surrounded by his wielder's thoughts was the worst kind of punishment.

Why was Ichigo so sad about this? Was he so childish that he did not understand that winning was not everything? The boy was going to live! What was there to be upset about? How did the Hollow expect Ichigo to defeat the actual Yhwach if he couldn't even defeat this captain who was at odds with his own power?

Some part of him, the part of him that wanted to protect Ichigo from the world's evil and from himself, hated feeling the rain. The other part hated knowing that he was somehow the cause for the weather. However, he knew that this was the best. He refused to admit to the fact that one day he would have to kill his wielder he have come to cherish. If only Ichigo never became a Shinigami, if only he would stop growing, if he could just find his limit, this wouldn't have to happen.

Damn he hated the rain.

 _How's the weather outside Yhwach?_ The Hollow mocked, as if this was all part of his malicious plan.

"I will do anything to protect Ichigo from the end of the world. If I must suffer through this rain, then so be it," the old man paused. He could feel the boy's heartbeat slow and his connection to his body fading. What was the Hollow waiting for?

 _What if I say that my way will not only protect the king, but also stop the rain?_

The old man raised an eyebrow. At this point, the rain had become heavier and the water had become to accumulate somehow in this odd world. It was beginning to become harder to ignore.

"What are you talking about Hollow?"

 _Bring the king in here. I'll keep his body stable for the time being, and I'll prove to you that he has the strength and potential to be the king. That's your main complaint with him, right? The fact that he's an arrogant prick? If I show you that you're just being a crap horse, I win. In return, you act like a proper partner. Fight with him, not against him, and make sure you actual do some protection until I can usurp you and be the power Ichigo needs._

"And how are you going to do that?"

The Hollow paused, but before long, he could feel the Hollow putting on a large grin.

 _The two of us never really did have a formal introduction, did we? We'll fight, but I'll pretend to be on your side for a little bit. If the king is a crap king because of who he is, then you have your way and Ichigo will forever be banned from using us. However, if he proves that he wants to work with us, and the fact that he's dying is your entire fault for a lack of communication on your end, he continues the fight. Deal?_

The old man considered his options. The Hollow would not be able to fix his blade until he got his own permission as well, so there goes all hope for him trying to backstab him. In addition, he would also get Ichigo into a stable condition until one of his friends found him.

Another part of him also reveled in the fact that it might form an alliance between himself and Ichigo that was strong enough to ensure his ward's safety even in the face of the true Yhwach. Finally, if all went well, the rain would stop as well.

"Fine then," he agreed, feeling the Hollow escape from his own subconscious and materializing in Ichigo's world. It had been a long time since he had seen the inverted form of his wielder and his insane smile. The Hollow just seemed happy to be back and about.

"I'm going to need that sword though," the Hollow requested as he pointed to the inverted blade of the true Zangetsu.

"Why? How is Ichigo going to fight if you will be wielding me?" the old man asked; however, the old man did not hesitate in giving the sword.

"Give him this. It's what my blade should have looked like if a shinigami, hollow, and quincy didn't decide to reside in the same castle all at once," the Hollow said as he tossed a sword into the air. Stretching his limbs, the pale boy played around with his blade. He was sure the Hollow has been training in wherever the boy goes when he's not out here, and the fact that he seemed more powerful than the last time they met was proof of that. He was going to have to hope Ichigo fails this test if he wanted his plan to work: he didn't have much time left given the Hollow's current strength. Soon, he would hardly be able to keep the Hollow reigned in.

After a second of making sure the Hollow was going to keep his word, Yhwach disappeared to appear to his wielder. Already he could tell that Ichigo's form was stabilizing. Despite his hatred for the beings, his high speed regeneration and hierro were very useful in the face of death. Although, it didn't help make his wielder look like a warrior as he laid on the floor bleeding out.

He walked slowly, unsure of what to say to Ichigo. As he said, they have never talked formally, and he wasn't sure what his wielder would think of this challenge. The boy was stubborn to the bone, enough so that he would rather die than think of losing this fight. The idiot. He almost rolled his eyes when he saw the boy's dumbfounded look at his appearance as the time around him slowed down.

"Do you want to fight?" he asked. He almost wanted to slap the boy for giving him such a dumbfounded look. Where was the resolve the Hollow always boasted about? Where was this pride?

"To live or to fight. Choose," he ordered, hoping he would choose the former. The boy mumbled something under his breath, but Yhwach made no effort to try and hear him. The longer he could manage to stay out here, the longer time he had to think of a way to loophole himself out of the Hollow's plan. The state the boy was in now was proof that he was nowhere near the level of Yhwach nor will he ever be at that level. He could feel the Hollow getting impatient with him from Ichigo's inner world, but he wouldn't let his wielder in unless he had the resolve to go through the Hollow's little challenge.

"It's pointless just to fight. It's pointless just to live," the boy began. Yhwach watched with interest as the boy pathetically tried to push himself up, as if he was a god about to give his blessing to continue on.

"I want to win!" he yelled at him, and the old man could practically see the smirk on the Hollow's face.

Yhwach stayed silent for a moment but did nothing else. "Fine," he said finally, "I shall take you there."

As his cloak enveloped Ichgio and transported them to the inner world, the old man began to regret his initial words to the boy. The Hollow was right, the boy had the resolve to go all the way. However, what use was the resolve if the boy did not have the strength to win? The boy was weak, and the old man prayed he was weak enough for the Hollow to beat him.

He sometimes wondered if Ichigo ever heard his own thoughts played back to him in this inner world. He also wondered if the Hollow could hear them as well. As he stood there watching the Hollow and Ichigo fight, he could hear the boy's prayers and wishes. He saw that the boy stole glances at him, even though the Hollow was quick to bring his attention on himself again.

As he thought, the Hollow was getting stronger, training. He hadn't known that the Hollow was able to think of new techniques of how to wield himself, even though the old man had initially thought the swinging of the blade was more of a game for the Hollow than an authentic sword technique.

 _I want to know how to borrow your power._ The old man heard from Ichigo's thoughts. He sighed. Since the boy had learned his blade's name, he had been blind to many of his fights due to Ichigo not seeking his assistance. He had knew the boy was a skilled fighter, skilled enough to deal with hollows himself, but had not realized that the boy would be able to keep up with the Hollow, even if the Hollow was simply playing around with him.

The Quincy power within Ichigo knew the boy's potential. Of course he would have. The old man had resided within Ichigo for years now, and somehow the Hollow had known Ichigo better than he had. Now the boy was begging for his forgiveness.

Was the price worth it to protect the boy?

 _We'll fight together again, old man!_ Ichigo promised, and Yhwach knew he was beat. He closed his eyes and was suddenly met with an odd sensation. He could feel himself within Ichigo's hands. He saw the blade coming towards him, and if he did nothing, the boy was going to die. The hands were ready to protect, and he allowed himself to be lifted. It was at that moment that he a strong power wash over him, as if he had the strength to protect everything in his domain. The old man opened his eyes again; unsure of what had just happened. The Hollow was playing it up masterfully, but he suspected he knew what was going on.

 _Does this mean you'll give me another chance?_ Some part of Yhwach scoffed at the notion: his powers were Ichigo if the boy asked for them. Another part wanted to deny Ichigo his powers: a Shinigami did not deserve life.

However, despite what part of him felt what, he knew one thing: he needed to protect the boy. If the Hollow had his way, the boy's spirit would be dead. Such was the way of Hollows, better off dead than not to win. At least, that was what it seemed initially. That final attack was too well plan for it to be seemingly random. Perhaps the Hollow could hear after all.

In a flash of light, the boy disappeared, just like he did when he first learned his blade's name. Except this time, the connection between himself and the boy did not fade almost immediately. Instead it stayed, and while it seemed to be growing weaker, the thread between them stayed, and somehow, he knew it would later evolve into a ribbon as they grew together.

"What did I tell you?" the Hollow asked with a large grin. Even after the battle, he looked as if he had only done a quick warm up. The Hollow looked at his broken blade with glee but quickly sobered as he heard sounds of the battle happening in the outer world.

"So, is that all?" the Hollow asked.

Yhwach, at first, didn't have much to say. He had lost the deal, and now he was expected to do his part. "Yeah, sorry to have bother you."

The Hollow tossed the broken blade behind himself, as if it was not a part of him at all. The Hollow saw the old man's shocked look, but he shrugged.

"No problem," the Hollow assured. He stretched his arms, knowing this was going to be one of the last times he could get out in a long time. "That guy is the king of this world after all. It'll be problematic if he doesn't win." Yhwach saw that little smirk on the Hollow's face. "So however unwillingly, I had to help."

The battle outside was beginning to get fierce, and if this little ordeal was as successful as he thought it was, Yhwach was going to be needed soon.

"Okay. I've done the job, so send me back already." Yhwach nodded and he could feel the Hollow tearing apart and the Hollow's shinigami power forming with him.

"He's strong, Zangetsu-san," the Hollow mocked. "Train him well, because one day, that power will become mine."

Yhwach sighed and vaguely felt the memory of their beginning drag him into his consciousness. He remembered seeing the true Zangetsu shift form before his eyes as Ichigo's Shinigami powers awakened. His form shifted less from a Hollow as his mask broke and the being wore the white Shinigami garb he was so accustomed to seeing now. Despite the change, he still called the being a Hollow as he was the reason Yhwach was in here in the first place, and the fact that he refused to admit he was sharing space with a Shinigami. However, despite being the boy's true source of power, the Hollow took one look at the old man and made a proposition.

" _Oi, Old Man Yhwach, was it? How about we have deal?"_

" _You protect the boy okay? Those guys out there are pretty strong, and I don't think me and Ichigo could take them all at once. You seem pretty strong though, so for now, you be Zangetsu. At least, until I get strong enough to protect all of us."_

Yhwach could still remember the disbelief he felt when he heard those words. A Hollow protecting them? It was unheard of. However, Yhwach knew better than to reject an offer like this. He was practically given control of Ichigo's power for the time being, and he managed to cut off Ichigo's connection to his Shinigami power, then the final battle could be prevented with the true Yhwach.

He did not expect himself to grow attached to the boy.

He did not expect himself to think he would want the boy to grow.

This little game just proved it all.

Yhwach, the man pretending to be Zangetsu for the time being, sighed and looked into the sky. Ichigo was calling for him, and he did not refuse the boy's call. If the boy was not going to back down from the face of danger, Yhwach resolved that he was going to do everything in his power to protect the boy.

Like the Hollow, Yhwach was going to be stronger.

He needed to if he was going to protect what was precious to him.

* * *

 **A/N:** Whew! Here's another one. I can't seem to escape the Rescue arc much, but I love that arc so much.

Here's a little fic about what would have happened if we knew Old Man Zangetsu was Yhwach from the start. Honestly, the hardest part of this fic was just getting names straight since he was one name one point and another at another point. To some extent, I miss just plain old Shirosaki, but I'm glad the Hollow has an official name now.

Thank you for reading!


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